A chipset in a PC (e.g., BGA, QFP, and CPU) may generate much heat when operating and it is necessary to dissipate the heat on time to avoid the degradation of the performance and the burn-out of the chipset. It is more important for a high-speed chipset generating much more heat. Hence, almost every host computer needs a heat sink device to dissipate all the heat generated by the chipset.
A heat sink device is commonly used for a higher speed chipset and installed by directly placing a heat dissipating plate with a plurality of fins on the chipset. A fan may also be used to assist heat dissipation. The heat generated by the chipset while operating is absorbed by the heat sink and the fan automatically turned on by the chipset under operation blows the heat sink and makes it cool down rapidly.
A heat-dissipating device in the prior arts is assembled with the chipset by using a metal plate to lock and fix the heat sink on the chip base (referred as socket). The above structure using a metal elastic plate to lock and fix the heat sink on the chip base is complicated and inconvenient to assemble. Therefore, such that the manufacturing cost increases and elasticity fatigue which causes the heat sink to malfunction occurs easily. Furthermore, the heat-dissipating device may be loosened while the computer is loaded and unloaded in delivery. The delicate and fragile chipset may be damaged if the operator asserts too much force. In addition, the metal elastic plate may have no place to lock if a BGA base instead of a chip base (socket) is used to connect the chipset and the motherboard, or the chipset is directly mounted on the motherboard.
The space between the chipset and the motherboard is only about 0.25 mm in height when the chipset is mounted on the motherboard. No manufacturer takes this limited space into consideration to improve the heat dissipation. An adhesive tape is generally used to attach the bottom of the heat sink and the top of the chipset, or a screw may be used to lock the heat sink on the motherboard. The adhesive tape, however, easily becomes aged and not adhesive under high temperature condition of operation. Therefore, some manufacturers require the motherboard vendor to reserve a hole for the screw. Using a screw has better performance than an adhesive tape but it is difficult in practice to reserve the hole for the screw because it may not be suitable for all designs of circuit layout, and not all motherboard vendors can reserve the hole on the motherboard. Additionally, the cost of assembling is higher. Consequently, manufacturing motherboards with a hole reserved for a screw to lock a heat sink is not popular.
FIG. 5 shows an improved structure disclosed in the prior arts to overcome the shortcomings in assembling a traditional chipset and a heat sink so as to accommodate all types of motherboards. The fix base A of the heat sink provided by the disclosed structure includes a hole A0 in the central part with four side plates. All on the four sides. The heat sink B is inserted upwards through the hole on the fix base A and then the plate body of the heat sink B stops at the edge of the hole A0. A fastening hook of the fix base clamps the two opposite sides of the chipset 3 in order to prevent the heat sink and the fix base from sliding and thereby fix them.
Although the above prior art can assemble and fix the heat sink and the fix base on the motherboard, the manufactured heat sink often has a rough bottom surface to which the chipset can not be tightly attached for dissipating heat efficiently. Each of the four sides has a side plate in the above structure. Two opposite sides are used to clamp two respective sides of the chipset and stop the two sides of the heat sink, and the other two sides cross the top of the heat sink. Thus, a slot B1 located between the fin of the heat sink through the two sides is needed. Four side plates of the fix base, however, are of the same height. Therefore, a slot hole B2 located on the slot of the heat sink to be inserted by the side plate is needed for the heat sink and the fix base be assembled. Thus, the other two side plates may be inserted through the slot hole to assemble the fix base and the heat sink when the two sides of the chipset are clamped by the side plates with fastening hooks. As a result, the efficiency of heat dissipation reduces due to reduction in the area for conducting heat after the slot hole is formed in the heat sink.